Podcast
Questions and Answers
What contributes the most to the large surface area for absorption in the intestine?
What contributes the most to the large surface area for absorption in the intestine?
- Villi and the presence of villi alone
- Length and folds in the mucosal lining (correct)
- Lack of peristalsis in the intestine
- Presence of digestive enzymes
Which of the following factors can decrease the bioavailability of tetracycline?
Which of the following factors can decrease the bioavailability of tetracycline?
- Combining with acidic foods
- Digestive enzymes in the stomach
- Presence of heavy metals in food (correct)
- Increased intake of high-fat foods
What effect does lying on the left side have on stomach emptying?
What effect does lying on the left side have on stomach emptying?
- Slows stomach emptying (correct)
- Accelerates stomach emptying
- Has no effect on stomach emptying
- Promotes absorption of drugs
What is a consequence of too rapid emptying of the gastrointestinal tract?
What is a consequence of too rapid emptying of the gastrointestinal tract?
How do antacid drugs generally affect the pH of gastric fluid?
How do antacid drugs generally affect the pH of gastric fluid?
Which of the following should NOT be done when administering sustained-release medication?
SELECT all that apply
Which of the following should NOT be done when administering sustained-release medication? SELECT all that apply
In what state are more lipid-soluble molecules typically found?
In what state are more lipid-soluble molecules typically found?
What is bioavailability in pharmacology?
What is bioavailability in pharmacology?
Which drug form typically offers faster dissolution in G.I. fluids?
Which drug form typically offers faster dissolution in G.I. fluids?
What effect does enteric coating have on a drug?
What effect does enteric coating have on a drug?
How does the nature of the absorbing surface affect drug absorption?
How does the nature of the absorbing surface affect drug absorption?
Which of the following factors primarily affects drug form on bioavailability?
Which of the following factors primarily affects drug form on bioavailability?
What characterizes passive transport of lipid-soluble drugs?
What characterizes passive transport of lipid-soluble drugs?
What characteristic do cell membranes primarily have that impacts drug absorption?
What characteristic do cell membranes primarily have that impacts drug absorption?
In the stomach, what state will a basic drug like codeine primarily be in?
In the stomach, what state will a basic drug like codeine primarily be in?
Which factor does NOT affect the surface area available for absorption in the intestine?
Which factor does NOT affect the surface area available for absorption in the intestine?
How does the administration of a tetracycline drug with an antacid affect the drug?
How does the administration of a tetracycline drug with an antacid affect the drug?
What is a common effect of food on drug absorption?
What is a common effect of food on drug absorption?
What will likely happen if a patient takes tetracycline with milk?
What will likely happen if a patient takes tetracycline with milk?
What is a characteristic of an acidic drug like aspirin in the stomach?
What is a characteristic of an acidic drug like aspirin in the stomach?
What primarily determines the rate and direction of diffusion across a membrane?
What primarily determines the rate and direction of diffusion across a membrane?
How does the ionization state of a drug affect its absorption in the gastrointestinal (G.I.) tract?
How does the ionization state of a drug affect its absorption in the gastrointestinal (G.I.) tract?
Which characteristic has the least influence on the absorption rate of a drug?
Which characteristic has the least influence on the absorption rate of a drug?
Why are basic drugs poorly absorbed in the stomach?
Why are basic drugs poorly absorbed in the stomach?
What happens to an acidic drug when it transitions from acidic to alkaline environments?
What happens to an acidic drug when it transitions from acidic to alkaline environments?
What is the relationship between drug molecule size and its ability to pass through membrane pores?
What is the relationship between drug molecule size and its ability to pass through membrane pores?
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Study Notes
Advantages of Oral Route
- Convenient and non-invasive method for drug administration.
- Allows self-administration without professional assistance.
- Generally less expensive than other routes.
G.I. Absorption
- Oral drugs must be absorbed from the G.I. tract into the bloodstream for effectiveness.
- Bioavailability is the metric for the amount of the drug that enters systemic circulation.
- Factors affecting absorption include drug form, nature of the absorbing surface, and G.I. system characteristics.
Drug Form and Preparation
- Dissolution rate impacts bioavailability; example forms include capsules, tablets, and liquid formulations.
- Enteric coatings prevent dissolution in stomach, released in the intestine; do not crush.
- Sustained-release forms must not be chewed or taken with hot/alcoholic beverages to prevent overdose.
Nature of the Absorbing Surface
- Drug absorption occurs through G.I. membrane, interstitial fluid, and capillary membrane.
- Membranes consist of lipid and protein layers; drug transport involves passive diffusion.
- Lipid-soluble drugs diffuse through cell membranes, while water-soluble drugs pass through membrane pores.
Chemical and Physical Characteristics of G.I. System
- pH of G.I. tract influences drug ionization; non-ionized drugs are lipid-soluble and easily absorbed.
- Aspirin, a weak acid, is non-ionized in the stomach—facilitating absorption.
- Basic drugs tend to become ionized in acidic environments, affecting absorption rates.
Surface Area for Absorption
- Intestines offer a larger surface area for drug absorption compared to the stomach due to folds and villi.
Impact of Food and Other Materials
- Certain foods and drug interactions can impede drug absorption; e.g., tetracycline with heavy metals in food.
- Delayed stomach emptying can slow drug absorption; causes include high-fat foods and body position.
- Changes in G.I. pH due to food or medications can adversely affect absorption location and rate.
Interactions and Implications
- Concurrent administration of certain drugs can decrease absorption efficacy; e.g., tetracycline with antacids forms insoluble complexes.
- Rapid G.I. tract movement lowers the amount of drug absorbed; slower movement allows for better absorption.
- Basic drugs like codeine are water-soluble in the stomach and poorly absorbed, while acidic drugs like aspirin are lipid-soluble and well absorbed.
Practical Considerations for Patients
- Instruct patients taking sustained-release medications to avoid chewing, crushing, or mixing with certain beverages.
- Educate on the potential adverse effects of combining antacids with specific antibiotics.
- Regular dietary considerations and timing with medications can optimize drug absorption.
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